Electric discharge device



Feb. 23, 1943. P. J. JOHNSON 2,312,246.

ELECTRIC DI S CHARGE DEVICE Filed May 12, 1939 Iflvntor: Percy IJ'ohrwsorw,

Patented Feb. 23, 1943 ELECTRIC DISCHARGE DEVICE Percy J. Johnson, Cleveland Heights, Ohio, assignor to General Electric. Company, a corporation of New York Application May 12, 1939, Serial No. 273,287

is Claims. (01. 176-122) electric discharge lamps having a gaseous atmosphere therein, such as a starting gas and mercury vapor. lates to an electrode construction for such electric discharge devices and lamps. The present application is a continuation-in-part of my application Serial No. 226,944, filed August 26, 1938.

- Gaseous electric discharge devices of the type referred to above generally consist of a pair of thermionic electrodes mounted within a sealed envelope containing a suitable starting gas and a metallic vapor, such as mercury vapor. When such a device is operated on alternating current, the electrodes alternately function both as anode and cathode. Th life of such electrodes, however, is ordinarily relatively short due to themtense ionic bombardment thereof during the period each electrode serves as the anode. Because of this ionic bombardment, and furthermore because of the high temperatures at which they operate, the electrodes sputter and vaporize, thus shortening the life of the device and causing blackening of the envelope. To partially overcome this difliculty, it has been customary to employ suitable shield means for each electrode, such shield means being electrically connected to an end of the electrode and acting to reduce the intensity of the aforementional ionic bombardment, thus prolonging the life of both the electrode and the discharge device.

In one type of circuit; employed for starting and operating gas-filled electric discharge devices having thermionic electrodes, one current supply wire of each electrode is connected to one of the terminals of a source of alternating current in series with a choke coil and a main switch, while the other current supply wires of the electrodes are interconnected by an auxiliary switch. After the electrodes have become sufficiently heated to support the arc discharge, the auxiliary switch is opened to thus initiate the arc discharge. It is thus evident that during operation of the discharge device only one end of each electrode is connected to the line or source of current, while the other end is open. To function properly, the electrode shield means or auxiliary anode must be connected to that end of the electrode which is connected to the source of current. Where it is possible to insert the discharge device in its supporting fixture in two or more positions, care must be taken to correctly insert the device so that the auxiliary anode is connected to the "hot side of the circuit, i. e., to the source of current supply; otherwise, the auxiliary anode will not function to reduce sputtering and vaporization of the electrode and to so increase the life of the discharge device. The necessity for noting the correct manner of insertion of the device in its fixture is Still more particularly, my invention resomewhat annoying and inconvenient, and this is particularly true in the case of a conventional fluorescent lamp where the coating of fluorescent material on the lamp envelope prevents one from observing to which lamp terminal the auxiliary anode is connected. According to my invention, I have overcome this difficulty by providing each electrode with a pair of auxiliary anodes electrically connected to opposite leads of the electrode whereby one or the other of said auxiliary anodes will always function as such, regardless of the manner in which the discharge device has been inserted in its supporting fixture.

One object of my invention is to provide a gaseous electric discharge device with a composite thermionic electrode so constructed and arranged as to reduce the ionic bombardment of the same to a minimum, and to operate at a relatively low temperature whereby sputtering and vaporization of the electrode, with consequent blackening of the bulb, is materially reduced and the life of the discharge device considerably increased.

Another object of my invention is to provide, for each of the thermionic electrodes of a gaseous electric discharge device, an auxiliary anode construction which will function as such regardless of the manner in which the discharge device has been inserted in its supporting fixture.

Still another object of my invention is to provide a pair of auxiliary anodes for each of the thermionic electrodes of a gaseous electric discharge device so formed and positioned with respect to said thermionic electrodes as to divide the current of the arc discharge to thereby reduce the ionic bombardment of the thermionic electrode and also the operating temperature thereof, but not sufficiently so as to interrupt the emission of electrons therefrom.

Further objects and advantages of my invention will appear from the following detailed description of a species thereof and from the accompanying drawing, in which Fig. 1 is a longitudinal sectional view of a gaseous electric discharge device provided with electrodes constructed in accordance with my invention; Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1; Fig. 3 is a diagrammatic illustration of a starting and operating arrangement for electric discharge devices of the type shown in Fig. 1; Fig. 4 is a fragmentary view, similar to Fig. 1,'of a modification of my invention;

- and Fig. 5 is a transverse sectional view taken on the line 5-5 of Fig. 4.

In the drawing, the invention is shown in connection with a gaseous electric discharge lamp gated tubular sealed container or envelope III of regular bulb glass and provided at each end thereof with an inwardly extending stem I I having a seal portion I2. A thermionic electrode I3 is mounted within the envelope III at each end thereof, each electrode I3 being supported by a pair of current supply or lead wires I4, I5 connected to opposite ends of the thermionic electrode and sealed into the seal portion I2 of the stem II. Each of the thermionic electrodes I3 comprises an arcuate shaped filamentary coil of a refractory metal, preferably tungsten, having a coating of an electron emissive substance thereon, such as, for instance, a mixture of barium and strontium oxides. Each end of the lamp envelope I is provided with a base I6 preferably secured to the envelope by suitable cement I1. Each base I6 is formed with a pair of contact terminals or pins I8 to which the electrode lead wires i4, i are connected. The lamp envelope ID has a gaseous filling therein consisting of a rare starting gas, such as argon, or a mixture of starting gases, and in addition contains a measured quantity IQ of a vaporizable substance such as mercury. During the operation of the lamp, the electrically excited mercury vapor emits both visible and ultra violet light rays. The quantity of mercury introduced into the lamp .envelope I0 is preferably such that it is only partially vaporized during the operation of the lamp, so that there is an excess of mercury present in thelamp. The lamp starts as a gas lamp and thereafter operates as a vapor lamp. The inner surface of the envelope III has a coating 20 of fluorescent material thereon, such as zinc silicate or calcium tungstate, which emits green and blue colored lights respectively when excited by radiation from the gaseous electric discharge during the operation of the lamp. The particles of fluorescent material are preferably applied to the in ner surface of the envelope Ill by using a suitable binding material, such as nitrocellulose and amyl acetate, which is then volatilized by heat treatment.

According to the invention, each electrode I3 is provided with an auxiliary anode construction comprising a pair of auxiliary anodes 2|, The auxiliary anodes 2I are made of a suitable metal, such as nickel, andare preferably made of wire of approximately 20 mil diameter bent into a U-shape. Each auxiliary anode 2| is provided with a leg portion 22 which is welded or otherwise secured to the electrode leads I 4, I5 to thereby support and electrically connect the anodes 2| to the said lead wires. As is evident from the drawing, the two auxiliary anodes of each pair are connected to the opposite lead wires I4, I5 of the associated electrode [3 immediately adjacent the ends of said electrode. Each auxiliary anode 2| is substantially semi-elliptical in shape, as shown in Fig. 2, and the two anodes of each pair are so disposed with respect to each other and with respect to the associated electrode I3 as to form the two halves of an ellipse encircling the said electrode I3, with the major axis of the ellipse extending substantially parallel to the plane of the electrode coil I3 and the plane of the ellipse disposed substantially at right, angles tothe longitudinal axis of the lamp envelope II). It should be understood, however, that the two auxiliary anodes 2| of each pair are separated or insulated As shown in Fig. 1, each pair of anodes 2I is located a relatively slight distance rearwardly of the associated electrode I3, 1. e., closer to the stem II than at least a portion of said electrode. so that the discharge path or distance between the two electrodes I3, I3 is somewhat less than the distance between the anodes 2| at opposite ends offthe lamp envelope. This particular disposition of the auxiliary anodes H is necessary in order that they may function to properly dividethe current of the arc discharge between the electrodes I3 and the anodes 2| themselves. If the anodes 2| were located too great a distance rearwardly of the electrodes I3, the entire current of the arc discharge would most likely flow through the electrodes I3 with the result that the operating temperature of said electrodes and the ionic bombardment thereof would be excessive, thereby greatly shortening the life of the lamp. On the other hand, if the anodes 2| were located in front of or in line with the forward extremities of the electrodes I3, then the major portion of, if not the entire, current of the arc discharge would likely pass through the auxiliary anodes, with the result that the operating temperature of the electrodes I3 would decrease to the point where the electrode would not be sufficiently electron-emissive to support the are discharge. I have found that by locating the auxiliary anodes 2| a distance of approximately between one-sixteenth to one-eighth of an inch rearwardly of the foremost extremity of the respective electrodes I3, the said anodes will divide the current of the arc discharge in the desired manner so that the operating temperature of the electrode I3 is reduced to a relatively low point, but not to the point where it becomes non-electron-emissive.

Referring to Fig. 3, illustrating diagrammatically the starting and operating circuit for the lamp described above, one of the lead wires of each electrode I3 is connected to the line or source of alternating current, in series with a choke coil 23 and a main switch 24, while the other lead wires of the electrodes are adapted to be interconnected through the medium of an auxiliary switch 25. Thus, in Fig. 3, the lead wire ll of the left electrode I3 is connected by conductor 26, through the choke coil 23, conductor 21, main switch 24 and conductor 28 to one side of the line, while the lead I4 of the other or right electrode I3 is connected by conductor 29 to the opposite side of the line. The lead wires I5 of the electrodes I3 are adapted to be interconnected by conductors 3B and 3| and the auxiliary switch 25. To place the discharge lamp in operation, both the main and auxiliary switches 24 and 25 respectively are closed so as to connect the thermionic electrodes I3 in series through the choke coil to the source of alternating current, with the result that the electrodes I3 are traversed by a current by which they are heated. When the said electrodes are preheatedto a temperature suflicient to activate the electron-emissive material thereon, the auxiliary in the previously described form of the invention,

During the period each electrode I3 acts as an anode, the arc discharge occurs partly between the cathode and the electrode l3 and partly between the cathode and that auxiliary anode M which is connected to the lead M or hot" side of the circuit. The are discharge current is thus divided between the electrode l3 and one of the associated auxiliary anodes 2|, thus reducing the cathode operating temperature and the intensity of the ionic bombardment previouslyreferred to, with resulting decrease in electrode vaporization and sputtering.

,The present commercial form of gaseous electric discharge lamps, such as shown in the drawing, is capable of insertion in its supporting fixture in either one of two different positions, thus the two anodes 32 of each pair are connected by their leg portions33 to the opposite lead wires 14, I 5 of the associated electrode l3 at a point closely adjacent the ends of said electrode. It will be noted from Fig. 4 that a portion of the electrode i3 extendsforwardly beyond the transverse plane deflned by the anodes 32. In other words, the two anodes 32 of each pair are located connecting the lamp into the operating circuit in two different ways. In one position, the electrode leads H are connected to the hot side (i. e., conductors 26, 29) of the operating circuit, as indicated in Fig. 3, while in the other position the lamp circuit connections are reversed 'from that shown in Fig. 3 so that the leads I 5 are connected to the hot side of the circuit and the leads M are connected to the circuit conductors 30 and 3| respectively. If only one auxiliary anode 2l were provided for each electrode l3, it would then be necessary either to note which lamp leading-in wire M or i5 the auxiliary anode was connected to, or to provide suitable indicating means therefor to thereby denote the correct manner of assembly of the lamp in its supporting fixture so as to insure the proper functioning of the auxiliary .anode during lamp operation.

However, by providing a pair of auxiliary anodes 2| for each electrode I3 and connecting the anodes of each pair to the opposite leading-in wires l4, of the associated electrode, in accordance with the invention, the lamp may be assembled in its supporting fixture in either one of the two different positions above referred to while still obtaining the proper functioning of the auxiliary anode construction. Depending on the manner of insertion of the lamp in its fixture, one or the other of the auxiliary anodes 2| of each pair will always function as such during lamp operation. In other words, that anode 29 of each pair which is connected to the hot side of the lamp circuit, 1. e., the circuit conductors 26, 29, will thus function as an auxiliary anode. It will, therefore, be evident that, with a lamp constructed according to my invention, there is no need of noting the proper manner of lamp assembly in its supporting fixture, thus greatly simplifying such assembly and insuring proper functioning of the auxiliary anode construction at all times.

In the modification shown in Figs. 4 and 5, each electrode 13 is provided with a pair of auxiliary anodes 32, 32 similar to the anodes 2! in Figs. 1 to 3 but difiering in shape therefrom. Thus, each anode 32 is in the form of a straight length of wire extending substantially transversely of the lamp envelope and substantially parallel to the plane of the electrode coil l3. As shown in Fig. 5, the two parallel anodes of each pair are disposed on opposite sides of the electrode l3 and are spaced a slight distance from the said electrode, i. e., at a distance of approximately between one-sixteenth to one-quarter of an inch. Each auxiliary anode 32 is provided with a leg portion 33 which is welded or otherwise secured to one or the other of the electrode leads l4, l5 to thereby support and electrically connect the anodes 32 to the said lead Wires. As

a relatively slight distance rearwardly of the associated electrode I 3, the same as the anodes 2| in Figs. 1 to 3 and for the same purpose, 1. e., to make the discharge path or distance between the two electrodes 13 at the opposite ends of the lamp envelope slightly less than the corresponding distance between their cooperating anodes 32.

What I claim as new and desire to secure by Letters Patent of the United States is: 1. A gaseous electric discharge device comprising a sealed envelope containing a gaseous atmosphere and having electrodes sealed therein, one of said electrodes. comprising a filamentary coil of a refractory metal having a coating of an electron-emissive material thereon and a pair of auxiliary anodes spaced from each other and electrically connected to opposite ends of said filamentary coil, said auxiliary anodes being disposed adjacent said filamentary coil and confined entirely rearwardly of a portion thereof whereby the said anodes are further removed from the other of said electrodes than the said portion of the filamentary coil electrode.

2. A gaseous electric discharge device com- I prising a sealed envelope containing a gaseous atmosphere and having a pair of electrodes sealed therein, each of said electrodes comprising a filamentary coil of a refractory metal having a coating of an electron-emissive material thereon and a pair of auxiliary anodes spaced from each other and electrically connected to 0pposite ends of said filamentary coil, said auxiliary anodes being disposed adjacent said filamentary coil and confined entirely rearwardly of a portion thereof whereby the respective pairs 1 of anodes are spaced farther apart than the said portions of the filamentary coils.

3. A gaseous electric discharge device comprising an elongated sealed envelope containing a gaseous atmosphere and having a pair of leading-in wires at each end thereof, and a composite electrode disposed within said envelope at each end thereof, each of said electrodes comprising a filamentary coil of a refractory metal having its opposite ends connected to the adjacent leading-in wires and provided with a coating of an electron-emissive material, and .an auxiliary anode structure comprising a pair of U- shaped wire elements spaced from each other and electrcally connected to the said adjacent leading-in wires, said U-shaped wire elements being disposed adjacent said filamentary coil with their open ends facing each other so as to substantially encircle said filamentary coil but located nearer the adjacent end of said envelope than a portion of said filamentary coil.

4. An' electrode for a discharge device comprising a filamentary coil of a refractory metal having a coating of an electron-emissive material thereon, and a pair of auxiliary anodes spaced from each other and electrically connected to opposite ends of said filamentary coil, said anodes comprising U-shaped wire elements disposed adjacent said filamentary coil with their substanrial thereon, and a pair of auxiliary anodes spaced from each other and electrically connected to opposite ends of said filamentary coil, said anodes comprising substantially straight wire elements extending substantially longitudinally of said filamentary coil and disposed closely adjacent to and on opposite sides of said coil, said straight wire elements also extending substantially parallel to each other and to .the plar'ieof. said filamentary coil, a portion of said coil projecting forwardly beyond the plane defined by said -wire elements.

6. A gaseous electric discharge device comprising an elongated sealed envelope containing a gaseous atmosphere and having a pair of leading-in wires at each end thereof, and a composite electrode disposed within said envelope at each end thereof, each of said electrodes comprising a filamentary coil of a refractory metal having its opposite ends connected to the adjacent leading-in wires and provided with a coating of an electron-emissive material, and an auxiliary anode structure comprising a, pair of substantially straight wire elements extending substantially longitudinally of said filamentary coil and substantially parallel to each other and to the plane of said filamentary coil, said straight wire elements being electrically connected to the said adjacent leading-in wires and being disposed on opposite sides of said filamentary coil and closely adjacent thereto but located nearer the adjacent end of said envelope than a portion of said filamentary coil.

7. A gaseous electric discharge device comprising a sealed envelope containing a gaseous atmosphere and having electrodes sealed therein, one of said electrodes comprising a filamentary coil of a refractory metal having. a coating of an electron-emissive material thereon and a pair of auxiliary anodes spaced from each other and electrically connected one to each end of said filamentary coil, said auxiliary anodes being disposed adjacent said filamentary coil and confined entirely rearwardly of a portion thereof whereby the said anodes are further removed from the other of said electrodes than the said portion of the filamentary coil.

8. A gaseous electric discharge device comprising a sealed envelope containing a gaseous atmosphere and having electrodes sealed therein one of which comprises a filamentary coil having a coating of an electron-emissive material thereon, and a pair of spaced conductors electrically connected one to each end of said filamentary coil and confined entirely rearwardly of a portion of said coil but disposed adjacent thereto, said conductors being located in a position sufficiently advanced with respect to another portion of said coil to function as anodes but not so far advanced that they prevent the said coil from being heated to effective electron emitting temperature during the operation of said device.

9. An electrode mount construction for a gaseous electric discharge device comprising a stem, a pair of leading-in wires sealed through said stem and extending forwardly thereof, a, filamentary coil extending substantially transversely between and electrically connected at its ends said coil projecting element.

to said leading-in wires, said filamentary coil but not so far advanced that they prevent the said coil from being properly heated to effective electron-emitting temperature during the operation of the discharge device.

10. An electrode for a discharge device, said electrode comprising a filamentary coil of a refractory metal having a coating of an electronemissive material thereon, and an auxiliary anode spaced from said filamentary coil and connected to an end of said coil, said anode comprising a straight wire'element extending sub stantially longitudinally of said filamentary coil and disposed substantially adjacent to said coil and parallel to the axis of said coil, 9, portion of forward beyond said wire 11; An electrode for a discharge device, said electrode comprising a filamentary coil of a refractory metal having a coating of an electronemissive material thereon, and an auxiliary anode comprising a metal element connected to one end of said filamentary coil and extending in the same general direction as said coil, said metal element being disposed closely adjacent said' filamentary coil, at least a portion of said coil projecting forwardly beyond said metal element.

12. A gaseous electric discharge device comprising an elongated sealed envelope containing a gaseous atmosphere and having a pair of leading-in wires at each end thereof, and a composite electrode disposed within said envelope at each end thereof, each of said electrodes comprising a filamentary coil of a refractory metal having its opposite ends connected to the adjacent leading-in wires and provided with a coating of electron-emissive material, and an auxiliary anodes structure comprising a metal element connected to one end of said filamentary coil and extending in the same general direction as said coil, said metal element being disposed closely adjacent said filamentary coil but located nearer the adjacent end of said envelope than at least a portion of said filamentary coil.

13. A gaseous electric discharge device comprising an elongated sealed envelope containing a gaseous atmosphere and having a pair of leading-in wires at each end thereof, and a composite electrode disposed within said envelope at each end thereof, each of said electrodes comprising a filamentary coil of refractory metal extending transversely of the axis of the envelope with its opposite ends connected to the adjacent leading-in wires and provided witha coating of electron-emissive material, and an auxiliary anode structure comprising a pair of metal wire-like elements electrically connected one to each end of said coil and extending in the same general transverse direction as said coil and on opposite sides thereof, said metal elements being disposed closely adjacent said coil and in a plane which is substantially perpendicular to the longitudinal axis of the envelope and passes through said coil.

PERCY J. JOHNSON. 

